"Hardcore" (1979) with George C. Scott is probably the best mainstream film ever made about the world of porn. It should be required XPT viewing. It was written by Paul Schrader, who also wrote "Taxi Driver" and "Raging Bull". Scott plays an uptight calvinist from Grand Rapids, MI (like Schrader) desperately trying to find his runaway daughter who started doing cheap porn. Tag line from the film - "oh my God, that's my daughter." Scott's performance is awesome, right up there with his work in "Patton", "Dr Strangelove" and "The Hustler".


trailer:

http://www.youtube.com/watch?v=5yU61GtjFN8&feature=related